Grinding machine



April 18, 1933. Fl s HAAS 1,904,045'

GRINDING MACHINE Filed Sept. 29, 1950 5 Sheets-Sheet l F. S. HAAS GRINDING MACHINE 5 Sheets-Sheet 2 Filed Sept. 29, 19,30

' Apri1 1s, 1933.

April 18, 1933. F. s. HAAs 1,904,045

GRINDI NG MACHINE Filed Sept. 29, 1930 5 SheetsSheet 5 prl 18, 1933. F, 5 MAASl y 1,904,045

GRINDING MACHINE Filed Sept. 29, 1930 5 SheetS-Sheet 4 Apr 8, i933. F. s HAAS 1,904,045

GRINDING MACHINE Patented Apr. 18, 1933 UNITED STATES PATENT oFFlcE* FREDERICK S. HAAS, OF CINCINNATI, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, T

THE HEALD MACHINE COMPANY, OF WORCESTEIM MASSACHUSETTS, A CORPORA- TION 0F MASSACHUSETTS GRINDING MACHINE Application filed September 29, 1930. Serial No. 484,953.

This invention relates to improvements in machine tools and especially to improvements in grinding machines.

In the use of automatic machines for -reducing the work to a predetermined, definite size wear on the tools must be taken care of in order that succeeding work pieces be iinj ished to the exact size of the preceding work piece. This is especially true of grinding machines since not only the reduction in size of the grinding wheel as a result of the normal wear from actually cut-ting away of the surface of the work but also the reduction in size of the wheel as a result of the retrueing of the Cutting face of a grinding wheel which is periodically dressed to maintain its face sharp and true must be considered. In the past this wear was taken up by manual adjustment of the grinding wheel or tool and the Work relative to one another which necessitated the constant washing and gauging ofthe work by the operator.

It is, therefore, one of the principal objects of the present invention to provide automatic means for compensating for the wear of the grinding wheel and to automatically adjust the work and wheel relative to one another to take up this wear.

Anoher obj ect of the invention is the provision of an automatic grinding machine for successively reducing a series of work pieces each to the same size within very close limits.

Another object of the invention is the provision of compensating means, as above noted, adjustable to compensate at a slow, line rate when the machine is being utilized for performing a finished surface on the work and for compensating at a fast or coarse rate when a rough or coarse grinding operation is being performed on the work, such as when roughing out the work.

Other objects and advantages of the present invention should be readily apparent by reference to the following specification considered in conjunction with the accompanying drawings forming a part thereof and it is to be understood that any modifications may be made in the exact structural details there shown and described within the scope of the appended claims without departing from or exceeding the spirit of the invention.

In the drawings:

Figure 1 is a front elevation of a machine embodying this invention.

Figure 2 is a transverse sectional view of the machine as seen from line 2-2 on Figure l.

Figure 3 is a sectional view transversely through the bed of the machine as seen from line 3-3 of Figure 1.

Figure 4 is a sectional view taken on line 44 of Figure 3.

Figure 5 is a sectional View taken on line 5-5 of Figure 3.

Figure 6 is' a sectional view taken on line 6-6 o f Figure 5.

Figure 7 is a sectional view taken on line 7-7 of Figure 1.

Figure 8 is a sectional view similar to that shown in Figure 3 but embodying certain modifications.

Figure 9 is an elevational view of certain parts shown in Figure 8 as ,seen from line 9 9 thereon.

Figure 10 is a sectional view taken on line 10-10 of Figure 9. v

Figure 11 is a sectional view taken longitudinally of the work head illustrating an automatic sizing device.

Figure 12 is a diagrammatic view of an hydraulic and electric circuit for use with this invention. l

The improved mechanism to be described and illustrated in the drawings is capable of application to all types of grinding machines for compensating for wheel wear and the like to insure the production of successive work pieces of the same size to within extremely close Jlimits, such as 'one or two ten thousandths of an inch. For the purpose of illustration there has been chosen and illustrated 'in the drawings an internal grinding machine to which the invention has been ap lied.

Throughout the several views oy the drawf ings similar reference characters are em` ployed to denote the same or similar parts.

In the drawingsthe reference character 10 indicates the bed of the Vmachine having formed at its upper end thereof in spaced we `parallel planes ways 11 and 12, the former supporting and guiding a wheel head 13 and the latter the work head 14. The wheel head 13 comprises a slide 15 supporting a motor 1 6 and journals 17 for the grinding wheel spindle 18 which has secured thereto the small diameter or internal grinding wheel 19. The slide 15 and parts carried thereby are adapted to be constantly reciprocated through a definite stroke by an hydraulic piston 20 reciprocable through a cylinder 21 carried by the bed 10 and the piston has extending from it a piston rod 22 coupled with the slide 15 through a bracket 23. The usual slide valve is employed Jfor directing the hydraulic pressure to'opposite ends of the cylinder 21 which valve is shifted through lever 24 pivotally mounted at 25 and oscillated about its pivot by adjustable dogs 26 secured to the slide 15.

The work head 14 comprises the slide 27 reciprocable longitudinally of the ways 12 by an hydraulic piston 28 contained within a cylinder 29 and the piston has extending from it a piston rod 30 secured through bracket 31 to the slide 27. A suitable valve is employed for directing the hydraulic pressure to opposite ends of the cylinder 29 which valve is shifted to a neutral position by a rock lever 32 secured'to one end of a shaft 33 which extends beyond the forward face of the bed 10 and the said rock lever 32 is actuated by adjustable dogs 34 secured to the forward end of the slide 27.

The slide 27 is shiftable between its limits of movement for shifting a work piece from the loading position to a position in operative association with grinding wheel 19 while the grinding wheel slide 15 is reeiprocable to .'eause the said grinding wheel 19 to traverse the work throughout its length thereby breaking up any possible grinding lines or the like on the work and equalizing the wear thereon, thus reducing the necessity for trueing of the wheel to a minimum. f

The work head 14 also includes a slide 35 having a dove-tailed guiding groove 36 formed therein receiving a similarly formed tongue or guide 37' extending from the slide 27 whereby the slide 35 is guided in its movement transversely of the slide 27 and of the bed 10. The said slide'35 has secured thereto' a bracket 38 supporting a work rest blade 39 having anangled top 40 for peripherally supporting the work 41 during its rotation. A workkrotation controlling or regulating wheel 42 is secured to a spindle 43 carried bythe slide 35 for frictional engagement with the work to control its rotation. The angled top 40 of the work rest blade 39 inclines toward the surface of the regulating wheel 42 for forming a work receiving ,troughtherewith ."in which the work 41 is positioned. Opposed' to the regulating wheel 42 and engaging the work 41 is a member 44, known as a pressure against the regulating wheel to maintain proper frictional contact between the wheel and work. The pressure roll 44 is secured to a shaft 45 rotatably supported by the slide 35 and is capable of limited lateral adjustment to permit the insertion and withdrawal of the work from the three-point work receiving throat formed by the pressure roll 44, work rotation controlling wheel 42 and work rest blade 39.

1n order to automatically place in and remove work from the work receiving throat the shaft 45 has loosely journaled thereon a work ejector'arm 46 having an operative connection with a gear segment 47 oscillatable about the axis of supporting shaft 48. Above the work receiving throat and pivoted at 49 to a bracket 50 extending upwardly from the slide 35 is a hopper or magazine 51 for holding unfinished work. A laten member or the like 52 prevents inadvertent discharge of the work from the magazine 51 which latch is released to permit discharge of the work from the magazine by the finished work as it is carried from the work receiving trough by the ejector arm 46.

F rom the foregoing description it will be noted that a machine has been provided for supporting a work piece and carrying same to and from the grinding position and which moved from the work receiving throat.

After the work and grinding wheel have been positioned in operative relation to one another the supplemental slide 35 is actuated transversely of the bed along the dove-tailed guide 37 to feed the work and wheel into one another and eii'ect a stock removal from the work. To this endy the slide 35 has rotatably but not translatably j ournaled therein a cross feed screw 53 having its threaded portion 54 threadedly received by a nut 55. A tongue 56 depends from the nut 55 and supports a stud 57 on which is mounted a roller 58. Carried by the lower slide 27 is a shaft 59 on which is oscillatably mounted a sleeve 60 having cam 61 extending therefrom. The cam 61 engages the roller 58 and as the cam oscillates the eccentric 62 thereof shifts the slide 35 to the left, as seen in Figures 2, 3 and 7 for Vfeeding the work carried lthereby into the grinding wheel. l1`he cam 61 and sleeve 60 i are oscillated by hydraulic pressure acting against opposite ends of a piston 63 having a sliding connection at 64 with the forked end 65 and 66 integral with and depending from the sleeve 60, as seen ingFigure 5. A piston valve 67 is provided for controlling and directing the hydraulic pressure source to the opposite ends of the piston63. The slide 35 is actuated by the cam 61 against the yielding pressure of the hydraulic pressure source which tends to reversely actuate the slide 35 and separate the wheel and work. This mechanism is illustrated in Figure 7 and comprises a cylinder 68 formed integral with or secured to the lower slide 27 having a piston 69 therein from which extends a plug or rod 70 engaging a fiange 71 depending from bracket 72 in which is journaled the worm shaft 73 for rotating the work rotation controlling or regulating wheel 42. The flange 71 of the bracketV 72 extends through an opening 74 provided in the lower slide 27 for this purpose. The shaft 43 of the regulating wheel. 42 derives its motion from the worm shaft 73 through a worm 75 and worm wheel 76 while the worm shaft 73 is driven through a pair of bevel gears 77 operatively coupled with the splined driving shaft 78. A pulley 79 secured to the driving shaft 78 transmits power thereto from any suitable or desirable source.

The piston or slide valve 67 is shifted in opposite directions by a pivotally mounted valve shifter arm 80 coupled on opposite sides with solenoids 81 and 82 whereby the said arm is oscillated about its pivot. The piston 63 is actuated in the direction for feeding the work into the wheel until the work has been reduced to the desired size at which time one of the solenoids 81 or 82 is energized for reversely shifting the valve 67 permitting the piston 69 to retract the slide 35 to its normal position and at the Sametime the valve controlling the flow of hydraulic medium to the cylinder 29 is reversed for retracting the wheel head from the grinding wheel to permit a replacement of the finished work in the work receiving throat.

As was noted above, the grinding wheel is constantly wearing during the grinding operation which wear must be compensated for during the feeding of the work into the wheel. For this purpose the piston 63 is provided on one side thereof with rack teeth 83. Fig. 5, meshing with the teeth of pinion 84 of compound gear 85. The other gear 86 of compound gear 85 meshes with a similar gear 87, Fig. 3, loosely journaled on sleeve or bushing 88. This bushing 88 surrounds the sleeve 89 ofratchet wheel 90. A flange 91 is secured to or formed integral with the gear 87 and has pivoted to it a pawl 92 for engagement with the teeth of ratchet wheel 90. A stud 93 is carried by the flange 91 forming a seat for spring 94 which abuts on its other end with the pawl 92 tending to actuate same about its pivot to maintain engagement between the pawl and ratchet. A throw-out screw 95 is carried by the walls of the surrounding housing for engagement with the other side of the pawl 92 for holding the said pawl out of engagement with the ratchet teeth against the yielding resistance of spring 94. The ratchet 90 and its sleeve 89 are keyed to one end of a vertical shaft 96 journaled in the housing or bracket 97 secured to and carried by the lower slide 27 L A bevel pinion 98 .is formed integral with or secured to the upper end of the shaft 96 and meshes with a similar bevel pinion 99 having a splined connection with the forward end 100 of cross feed adjusting screw 54.

As the piston 63 is actuated for oscillating the cam 61 to feed the slide 35 the compound gear 85 is rotated causing a similar rotation of gear 87 and pawl 92. This movement of pawl 92, while in engagement with the teeth of the ratchet 90. rotates said ratchet and vertical shaft 96 forrotating the screw 54 and adjusting the slide y35 relative to the nut 55 held against movement by the cam 61. This movement, however, takes place only in the event that the work has not been reduced to size p-rior to the engagement of the pawl 92 and ratchet 90.

To control the size of the work use is made of an automatic mechanism shown in Figure 11 which comprises a housing 101 having rotatably and slidably mounted .therein a` shaft 102 carrying at its forward end a contact 4point 103 for engagement with the surface of the work being ground or finished. A spring loaded plunger 104 is mounted in the housing 101 and contacts at its upper end' with arm 105 of bell crank 106 pivoted at 107 in the walls of the housing 101. The other arm 108 of the bell crank is received in a circumferential groove 109 in the shaft 102. Secured to the rear of the shaft 102 is aswitch closer or'- arm 110 for closing the make and break switch 111. The switch 111 is electrically connected with one of the solenoids 81 or 82 for properly shifting the slide valve 67 to connect the hydraulic pressure source with the proper side of piston 63 to retract the cam 61 from the roller 58 so that the hydraulic pressure in cylinder 68 through the piston 69 will actuate slide 35 to disengage the work and the grinding wheel. At the same time solenoid 112 is energized for shift ing valve 113 to connect the hydraulic pressure with cylinder 29 to actuate the piston 28 therein for retracting the work head 14 to its work ejecting and loading posftion. After f and work at the completion of the previous n grinding operation.

The sizing device 'shown in Figue 11 is positioned adjacent the surface of the work being operated upon by suitable-'automatic means not disclosed in the drawings or here described since it forms no part of the present invention. As shown in Figure 12 the Work head may be returned to its position adjacent the operative face of the grinding wheel by closing a switch 118 at the end of its stroke which completes an electrical circuit including a solenoid 119 for reversely shifting the valve 113. A similar switch 120 may be closed by the work head when it reaches its operative position for completing an electrical circuit which includes one of the solenoids 81 or 82 for shifting the valve 67 to effect a relative movement between the work supporting slide and wheel, one toward the other.

As shown in Figure 3 the compensator mechanism or pawl and ratchet 92 and 90 are shown within the bed in a very inaccessible position and it will be noted that the same feed or movement is imparted to the vertical shaft 96. In Figure 8 a modification of the invention is disclosed in that the compensating mechanism -is made variable or selective and is positioned in a more accessible part of the machine tool organization so as to be within convenient reach and control-of the operator. To this end an adjusting screw 121 is extended beyond the forward surface of the upper slide 35 and is further provided with an internal bore through which splined shaft 122 extends. The splined shaft 122 and the screw 121 are rotatably but non-translatably mounted in the slide 35 and a housing 123 secured thereto. The splined shaft 122 has slidable thereon a bevel gear '124 meshing with a complementary bevel gear 125 on the u per end of vertical shaft 126. A pinion 127)'Iis keyed or otherwise secured to the lower end of the shaft 126 and meshes with the gear 86 of compound gear 85 operable by the piston 63 whereby the said vertical shaft 126 obtains its rotation. Secured to the hollow adjusting screw 121 at its forward end within the housing 123 is a pair of ratchets 128 and 129. one for coarse adjustment and the other for fine adjustment. A carrier plate 130 is keyed or otherwise secured to the end of the splined shaft 122l and has .A pivoted thereto at 131 a pair of pawls 132 and 133, the former for engagement with the ratchet 128 and the latter with the ratchet 129. A spring pin 134 is also car` ried by the carrier plate 130 and supports springs 135 which engage the pawls 132 and 133 tending to actuate same in a counter clockwise direction to maintain engagement between them and their respective ratchets.

Each pawl has a finger 136 extending there- 'from for engagement, with their respective adjusting screws 137 and 138.

The operation ofthe modified structure 1s substantially the same as that described above except that throughthe adjusting screws 137 and 138 the rate of adjustment orv movement of the screw 121 may be controlled or the adjustment may be selected depending on whether roughing or finishing grinding operations are being performed upon the work then in the machine. v f

The adjusting screw 54, above described, is provided on its forward end with an operating wrench portion 139 which has an angular cross section whereby the screw 54 may be manually actuated when the pawl carrier pla-te 91 is in the proper position for engaging the pawl 92 with the lock-out screw 95. In the modified structure disclosed in Figures 8 to 10 inclusive the pawls may be disengaged from the ratchets at the will of the operator by simply turning the adjusting screws 137 and 138 in such a direction as to actuate the pawls clockwise of their pivot 131. To manually adjust the screw 121 it is provided with a gear pinion 14() meshing with aV second pinion 141 mounted interiorly of the housing 123 on a stud 142 extending therethrough. The stem of the pinion 141 whichsurrounds the stud 142 is provided with flat surfaces 143 for the reception of the socket portion of an actuating wrench or the like.

rThe operation of the device should be readily understood by refe-rence to the foregoing description and a further detailed explanation of its operation is deemed unnecessary.

I claim:

l. In a machine of the character described the combination with a bed and a grinding wheel supported thereby, of a work holding unit for presenting work in opposition to the grinding wheel and means for imparting Arelative feeding movement to said unit and wheel including an oscillatable cam disposed in nontranslatable relation to one of said parts and a cam follower carried by the other of said parts and shiftable therewith on movement of the cam, hydraulic means for oscillating the cam to effect said movement, and means for yieldingly urging the follower into engagement with the cam, said means including a cylinder and a hydraulically actuable piston movable in the cylinder and having a portion engaging the follower bearing member.

i 2. In a machine of the character described the combination with a bed and al grindingl wheel supported thereby, of a work holding unit for presenting work in opposition to the grinding wheel and means for imparting relative feeding movement to said unit and wheel including an oscillatable cam disposed in nontranslatable relation to one, of said parts and a cam follower carried by the other of said parts and shiftable therewith on movement of the cam, hydraulic means for yieldingly urging the follower into engagement with the cam, said means including a cylinder and a hydraulicallv actuable piston movable in the cylinder and having a portion engaging the follower bearing member, and means for man# ually adjusting the follower with respect to the unit controlled thereby.

3. In a machine of the character described the combination with a bed and a grinding wheel supported thereby, of a work holding unit for presenting work in opposition to the grinding wheel, and means for imparting relative feeding movement to said unit and wheel including an oscillatable cam disposed in nontranslatable relation to one of said arts, a cam follower carried by the other of said parts and shiftable therewith on movement of the cam, hydraulic means for oscillating the cam to effect said movement, and means for automatically adjusting the position of the follower with respect to the unit controlled thereby to compensate for wea-r of the grinding member and insure proper presentation of successive work p-ieces thereto.

4. In a machine of the character described the combination with a bed and a grinding wheel supported thereby, of a work holding for presenting work in opposition to the grinding wheel and means for imparting relative feeding movement to said unit and wheel including an oscillatable cam disposed in non-translatable relation to one of said parts, a cam follower carried by the other of said parts and s hiftable therewith on movement of the cam, hydraulic means for oscillating the cam to eect said movement, and means for automatically adjusting the position of the follower with respect to the unit controlled thereby to compensate for wear of the grinding member and insure proper presentation of successive work pieces thereto, said means including a rack shiftable on oscillation of the cam, a pinion rotated by oscillation of the rack, a pawl and ratchet mechanism one of said parts being oscillated by movement of the pinion, and a feed screw associated with the other of said parts whereby excessive oscillation of the one of said parts will cause interengagement of a progressively advanced portion of the ratchet with the pawl and reverse oscillation will carry the parts around as a unit to rotate the screw to shift the cam Jfollower with respect to the unit associated therewith.

5. In a machine of the character described the combination with a bed and a' grinding wheel supported thereby, of a work holding unit for presenting work in opposition to the grinding wheel, means for imparting relative feeding movement to said unit and wheel including an oscillatable cam disposed in nontranslatable relation to one of said partsand a cam follower carried by the other of said parts and shiftable therewith on movement of the cam, hydraulic means for oscillating ythecam to effect said movement, and means for automatically adjusting the position of the follower with respect to the unit controlled thereby to compensate for wear of the grinding member and insure proper presentation of successive work pieces thereto, said mechanism including a rack shiftable on oscillation of the cam, a pinion rotated by oscillation of the rack, a pawl and ratchet mechanism, one of said parts being oscillated tion thereof, whereby the screw may be inde-` pendently,manually adjusted.

6. In a device of the classdescribed, the combination of a bed, a grinding wheel rotatably carried thereby, a work supporting slide carried by the bed for movement transversely thereof to effect a relative feed between the work and grinding wheel, an adjusting screw carried by the slide, a nut on the screw, hydraulically actuable means for engagement with the nut for axially shifting same and parts connected therewith, and means for rotating the screw to effect an additional movement of the nut and the parts.

7. IIn a device of the class described, the combination of a bed, a grinding wheel rotatably carried thereby, a work supporting slide carried by the bed for movement transversely thereof to eifecta relative feed between the work and grinding whe`el, an adjusting screw carried by the slide, .a nut on the screw, hydraulically actuable means for engagement with the nut for axially shifting same and parts connected therewith, said hydraulic means comprising a piston, a pivotally mounted arm operatively connected with the piston for oscillation about its pivot,

.and a cam operable by the arm, and means for rotating the screw to effect an yadditional movement of the nut and the parts.

8. In a grinding machine, the combination of a bed, a grinding wheel carried thereby, a work supporting member carried vby the bed for movement transversely thereof to effect a relative feed between the grinding wheel and work, means for effecting said relative movement comprising an hydraulically actuated piston, a pivotally mounted arm oscillatable by the piston, a cam oscillatable by the arm, an adjusting screw rotatably carried by the slide, a nut on the slide, an abutment on the Anut for engagement with the cam whereby oscillation of the cam shifts the nut and parts carried thereby to feed the work supporting slide and grinding wheel relative to one another, and means for rotating the adjusting screw to advance the nut relative to the screw and shift the slide an additional amount.

9. In a grinding machine, the combination of a bed, a grinding wheel carried thereby, a work supporting member carried by the bed for movement transversely thereof to effect a relative feed between the grinding wheel and work, means for effecting said relative movement comprising an hydraulically actuated piston, a pivotally mounted arm oscillatable by the piston, a cam oscillatable by the arm, an adjusting screw rotatably carried by the slide, a nut on the slide, an abutment on the nut for engagement with the cam whereby oscillation ofthe cam shifts the nut and parts carried thereby to feed the work supporting slide and grinding wheel relative to one another, and means for rotating the adjusting screw to advance the nut relative to the screw and shift the slide an additional amount, said means comprising 'a rack on the piston, a ratchet and pawl mechanism operable by the piston rack, and means between the pawl and ratchet mechanism and the adjusting screw for rotating the said screw thereby.

10. In a grinding machine, the combination of a bed, a grinding` wheel carried thereby, a work supporting member carried by the bed for movement transversely thereof to effect a relative feed between the grinding wheel and work, means for effecting said relative movement comprisingA an hydraulically actuated piston, a pivotally mounted arm oscillatable by the piston, a cam oscillatable by the arm, an adjusting screw rotatably carried by the slide, a nut on the slide, an abutment on the nut for engagement with the cam whereby oscillation of the cam shifts the nut and parts carried .thereby to feed the work supporting slide and grinding Awheel relative to one another, and means for rotating the adjusting screw to advance the nut relative to the screw and shift the slide an additional amount, said means comprising a rack on the piston, a ratchet and pawl mechanism operable by the piston rack, means betweenvthe pawl and ratchet mechanism and the adjusting screw for rotating the said screw thereby, and means for locking the pawl and ratchet out of engagement to permit a manual actuation of the screw.

11. In a grinding machine of the class described, the combination of a bed, a grinding wheel rotatably mounted thereon, a work supporting unit for supporting a work piece for operatlon thereon by the grinding wheel, and means for feeding the work supporting unit toward the grinding wheel and compensatingfor wheel wear eomprisinga hollow screw journaled in the unit, a shaft extending through the hollow screw, a nut on the screw, means engaging the nut andoscillatable relative thereto for effecting an axial movement of the nut and parts connected therewith, and additional means for rotating the shaft to advance the screw relative to the nut to thereby change the movement of the slide.

12. In a grinding machine of the class described, the combination of a bed, a grinding wheel rotatably mounted on the bed, a work supporting slide mounted thereon for movement toward and from the grinding wheel, means for actuating the slide including a hollow screw rotatably journaled thereon, a nut on the screw, an oscillatable cam for engagement with the nut and veffecting an axial movement thereof together with the parts connected therewith, a shaft rotatably mounted within the hollow screw, and means for rotating the shaft and thereby incrementally rotating the screw and advancing the same relative to the nut;

13. In a grinding machine of the class described, the combination of a bed, a grinding wheel rotatably mounted on the bed, a work supporting slide mounted thereon for movement toward and from the grinding wheel, means for actuating the slide including a hollow screw rotatably journaled thereon, a nut on the screw, an oscillatable cam for engagement with the nut and eiecting an axial -movement thereof together with the parts connected therewith, a shaft rotatably mounted within the hollow screw, means for rotating the shaft and thereby incrementally rotatin A the screw and advancing the same relative to the nut, and means between the shaft and screw whereby a given rotation of the shaft will advance the screw at differential amounts.

14. In a grinding machine of the class described, the combination of a bed, a grinding wheel rotatably mounted on the bed, a work supporting slide mounted thereon for movement toward and from the grinding wheel, means for actuating the slide including a hollow screw rotatably journaled thereon, a nut on the screw, an oscillatable cam for. engagement with the nut and Aeffecting an axial movement thereof together with the parts connected therewith, a shaft rotatably mounted within the hollow screw, means for rotating the shaft and thereby incrementally rotating the screw and advancing the same relative to the nut, means between the shaft and screw whereby a given rotation of. the shaft will advance the screw at differential amounts, said means including a coarse toothed ratchet and a fine toothed ratchet, a pawl for each ratchet, and means for positively disconnecting one of said pawls from its ratchet.

15. In a grinding machine of the class described, the combination of a bed, a grinding wheel rotatably mounted thereon, a pair of superimposed slides mounted on the bed for translation relative thereto to operatively associate a work piece carried thereby with the grinding wheel, means for translating the slides as a unit, means for shifting one of the slides laterally of the other slide for effecting a relative feed between the grinding wheel and work, said means including an oscillatable cam operable through a given zone and means for advancing the said slide in a direction toward the grinding wheel an Loomis amount to vary the zone of operation of the cam to compensate for wheel wear.

16. In agrinding machine of the class described, the combination of a bed, a grinding wheel rotatably mounted thereon, a pair of slides superimposed on one another mounted on the bed for translation relative thereto to operatively associate a work piece carried thereby with the grinding wheel, hydraulic means for translating said slides as a unit, hydraulic. means for shifting one of said slides relative to the other to effect a feed between the grinding-wheel and work including a piston, an arm oscillatable thereby, a cam associated with the arm for movement therewith, an abutment on the slide :for enga-gement with the cam, and hydraulic means for yieldingly resisting lateral movement of the slide, maintaining contact between the abutment and cam and reversely laterally shifting the said slide to separate the work and grinding wheel at the conclu.- sion of the grinding operation. v

17. In a grinding machine of'the class described, the combination'ot` a bed, a grinding wheel rotatably mounted thereon, a pair of slides superimposed on one another mounted A on the bed for translation relative thereto to operatively associate a work piece carried thereby with the grinding wheel, hydraulic means for translating said slides as a unit,

hydraulic means for shifting oneof said slides relative to the other to eect a feed between the grinding wheel and work including a piston, an arm oscillatable thereby, a cam associated with the arm for movement therewith, an abutment on the slide for engagement with the cam, hydraulic means for yieldingly resisting lateral movement of the slide, maintaining contact between the abutment and cam and reversely laterally shifting the said slide to separate the work and v grinding wheel at the conclusion of the grinding operation, said cam having a definite throw for shifting the slide through adefinite zone, means for-automatically stopping the oscillation of the cam when the work is reduced to the desired size, and means for shifting the slide relative to the zone of operation of the cam to compensate for wear on the grinding wheel to insure the automatic stopping of the cam oscillation when successive pieces are reduced to the desired size.

18. A' feeding mechanism for use with grinding machines comprising a work supporting slide advanceabletoward a rotating grinding wheel, a member on theslide movable therewith and4 relative thereto, an oscillatable cam for engagement with said member for shifting same and the slide, automatic means for interrupting the movement of the slide and stopping the oscillation of the cam V- when the work has been reduced to the de- 

